The present invention relates to locks, and more particularly to an anti-tampering mechanism for the ignition lock of an automobile.
Various types of locks for use in connection with the ignition circuit of an automobile are known in the art. Many of such locks include anti-theft and/or anti-tampering mechanisms which are incorporated to deter unauthorized use of automobiles. One such lock is disclosed in U.S. Pat. No. 5,202,580. The lock includes a Hall effect sensor dement which is activated by a control magnet on the cylinder of the lock so that when the cylinder is rotated by a key to its start position, the Hall effect sensor element is activated. The activation of the sensor element provides one of several starting criteria to an ignition circuit for starting an automobile. An anti-tampering magnet on the cylinder lies directly under the sensor element in the off position and biases the Hall effect sensor element to its off position so hard that other magnetic forces induced from the exterior of the lock cannot overcome the bias and activate the sensor.
Other anti-theft and/or anti-tampering mechanisms which utilize magnetic elements are shown in U.S. Pat. Nos. 4,862,139 and 4,546,266. Although many of such devices are effective for their intended purpose, there remains a need for improved devices of this type.